Methods of migrating data between storage apparatuses

ABSTRACT

A data migration system is provided for migrating data between an existing file server apparatus and a new file server apparatus in a computer system that includes a plurality of host computers and a plurality of file server apparatuses that are mutually connected to one another. The data migration system on the new file server apparatus copies file attributes unique to the network attached storage (NFS) and file attributes unique to the common internet file system (CIFS) from the existing file server apparatus, and stores the file attributes without changing the file attributes in the new file server apparatus. Then actual data is moved from the existing file server to the new file server. When a file access to data is made from a host computer during the file migration process, and if the data has not been migrated from the existing file server to the new file server, the data is read out from the existing file server onto the new file server, and the file access is processed by the new file server as if the existing file server were processing the file access.

FIELD OF THE INVENTION

The present invention relates to data access methods to be implementedin storage apparatus systems in information processing systems, and inparticular, to methods of migrating data between storage apparatuses.

DESCRIPTION OF RELATED ART

Computer systems used in banks and corporations require large-scalestorage apparatus as voluminous amounts of data are handled. Moreover,as these data are increased on a daily basis it becomes necessary toexpand the storage apparatus or replace them with larger capacitysystems. The normal means to replace a storage apparatus is by usingmagnetic tapes, etc. to back up the system (existing storage apparatus)and restoring the data into the new storage apparatus (new storageapparatus.)

However, in order to perform the back up it is necessary to temporarilysuspend the operation of the I/O devices of the host computers. And, thesuspension period is generally long. This stoppage time increases as thestorage capacity increases. Also, in this type of a large-scale systemthe norm is to operate the system 24 hours a day without stopping. And,since replacing the storage apparatus also requires 24 hour operation,it would pose a problem to perform the back up by suspending I/O deviceson the host computers side.

A method for providing on-line data migration from an existing storageapparatus to a replacement storage apparatus has been proposed. Whendeploying a new storage apparatus in a system that has been initiallyoperated by the host computer and storage apparatus (existing storageapparatus), the new storage apparatus simultaneously receives read-writeaccesses from the host computer while migrating the data from theexisting storage apparatus to the new storage apparatus. Morespecifically, when migrating data from the existing to the new storageapparatus, the connection between the host computer and the existingstorage apparatus is temporarily cut off, and the host computer isconnected to the new storage apparatus. The new storage apparatus isalso connected directly to the existing storage apparatus. The newstorage apparatus makes it possible to migrate data between the storageapparatuses in a manner transparent to the user as the new storageapparatus is provided with a function to copy data of the existingstorage apparatus to the new storage apparatus and a function to makeitself look like the existing storage apparatus to the host computer.

In recent years, there has been a proliferation of storage apparatusescalled Network Attached Storages (NASs), which are directly connected toa local area network (LAN) that mutually connects to several hostcomputers. A NAS and the respective host computers exchange data with anetwork file access protocol such as Network File System (NFS). The NFShas stipulated commands necessary for file accesses such as those forreading/writing files and creating/deleting files. Because of this, bycombining these commands, it is possible to copy data from one NAS(existing NAS) to a new NAS.

Simple data copying is fully possible even in NAS by using the methoddescribed above. However, when data is migrated from a NAS, attributeinformation attached to the data may pose a problem. File names, fileowners, the creation date of files and the access times are written infiles. When copying files from the existing NAS to the new NAS, the mereoperation of simply reading out the files from the existing NAS andcopying the files to the new NAS would alter the file creation dates andthe time they were accessed. Thus, it is not possible to migrate datawhile retaining the state of the existing NAS. Moreover, for accessesbetween a NAS and a host computer, it is possible to made data accesseswith several types of access protocol.

For example, many NASs support NFS and Common Internet File System(CIFS). The file attributes of the respective protocols have items thatare shared as well as those that are not. Because of this, if files areread from an existing NAS with an NFS protocol, only the file attributesaccording to NFS can be extracted, but the migration of file attributesin CIFS protocol is not possible.

SUMMARY OF THE INVENTION

The present invention provides NASs with a system that is capable ofmigrating complete data in a manner transparent to the host computersand users.

A computer system in accordance with an embodiment of the presentinvention includes a host computer, a first file server apparatus and asecond file sever apparatus. While the host computer, that is connectedto the first file server apparatus, initially performs input and outputoperations, the connection between the host computer and the first fileserver apparatus is temporarily severed when data is migrated from thefirst file server apparatus to the second server apparatus. Then, thehost computer is connected to the second file server apparatus, and thefirst file server apparatus is connected to the second file serverapparatus.

Migration of data from the first file server apparatus to the secondfile server apparatus is performed in the following manner. First, thesecond file server apparatus first reads out a directory tree structureof the first file server apparatus, and read out all of the files in thefirst file server apparatus by using the directory tree structure. Thefiles thus read are successively written into the second file serverapparatus.

In one embodiment, the date migration is realized by the second fileserver apparatus reading out files and file attributes from the firstfile server apparatus, and writing the results into the second fileserver apparatus. As the second file server apparatus writes the fileattributes, date information written in the first file server apparatusare stored in the second file server apparatus without being changed.

When the first and second file server apparatuses support a plurality offile access protocols, the second file server apparatus performs readingand writing operations for file attributes of one file in a plurality oftimes. For example, when two types of access protocols are supported,the read and write operations of file attributes are performed twice.

Also, when there are file accesses from the host computer during datamigration, the second file server apparatus processes the file accesses.For example, when the host computer makes a file read access to read afile on the first file server apparatus when the file has not beenmigrated to the second file server apparatus, the file is first migratedfrom the first server apparatus to the second file server apparatus, andthen the second server apparatus accepts the read access from the hostcomputer. If the migration of a file has been completed when the hostcomputer makes a read access to the file, the second file serverapparatus will directly process the read request from the hosts.

Other features and advantages of the invention will be apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings that illustrate, by way of example, variousfeatures of embodiments of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an example configuration of a computersystem in accordance with one embodiment of the present invention.

FIG. 2 shows a file/directory structure of the present invention storedin an existing file server apparatus and a new file server apparatus.

FIG. 3 shows a structure of a meta data structure of a file system ofthe present invention stored in a disk of a new file server apparatus

FIG. 4 shows a flowchart of a data migration process for migrating dataperformed by a migration module in accordance with an embodiment of thepresent invention.

FIG. 5 shows a flowchart of a migration process for migratingfile/directory attribute information which is performed by the migrationmodule.

FIG. 6 shows a flowchart of a file data migration process for migratingactual files, which is performed by the migration module.

FIG. 7 shows a flowchart of processes performed by the migration module,which are performed when a host computer issues a file read requestwhile the migration module is processing.

FIG. 8 shows a flowchart of processes performed by the migration module,which are performed when a host computer issues a file write requestwhile the migration module is processing.

FIG. 9 shows a data structure of log data that is used by a new fileserver apparatus in accordance with the present invention.

FIG. 10 shows a flowchart of reflection processes for log data which areperformed by the migration process.

FIG. 11 shows a flowchart of reflection processes for log data which areperformed by the migration process.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of an example configuration of a computersystem in accordance with an embodiment of the present invention. Thecomputer system includes hosts (e.g., a host 1, a host 2, and the like),an existing file server apparatus 3, a new file server apparatus 4 andan Ethernet switch 5.

The host 1 has a Network File System (NFS) client program 11 and anapplication program 12. The application program 12 accesses the existingfile server apparatus 3 or the new file server apparatus 4 via the NFSclient program 11. Also, the host 2 has a Common Internet File System(CIFS) client program 21 and an application program 22, the applicationprogram 22 accesses the existing file server apparatus 3 or the new fileserver apparatus 4 via the CIFS client program 21.

The existing file server apparatus 3 consists of interfaces 31, 32, astorage device (e.g., a storage disk) 33 and a controller apparatus 34.The new file server apparatus 4 consists of interfaces 41, 42, a storagedevice (e.g., a storage disk) 43 and a controller apparatus 44. Theexisting file server apparatus 3 is connected to the hosts 1 and 2 fromits interface 31 via the Ethernet switch 5, while the new file serverapparatus 4 is connected to the two hosts from its interface 41 via theEthernet Switch 5. Also, the existing file server apparatus 3 and thenew file server apparatus 4 are mutually connected to their interfaces42 and 32, respectively, via an Ethernet cable 6.

The controller apparatus 34 has an NFS processing module 341 and a CIFSprocessing module 342 and a file system section 343. It is noted that,in the present embodiment, each module is a functional unit of theprogram that is read into and executed by the controller apparatus 34.The NFS processing module 341 processes the file access request from thehost 1, while the CIFS processing module 342 processes the file accessrequest from the host 2. The file system section 343 performs read andwrite processes for files within the disk 33. When the NFS processingmodule 341 or the CIFS processing module 342 receives a file readrequest, the file system section 343 takes over the request and extractsfiles to be read and file attribute information of the files from thedisk 33 and delivers them to the NFS processing module 341 or the CIFSprocessing module 342. When a write request is received, the filesreceived by the NFS processing module 341 or the CIFS processing module342 are written into the disk 33.

Similarly, the controller apparatus 44 has a NFS processing module 441,a CIFS processing module 442 and a file system section 443. Thesegenerally perform the same operations as the NFS processing module 341,the CIFS processing module 342 and the file system section 343. Also,the controller apparatus 44 has a migration module 444 that performsmigration of data from the existing file server apparatus 3 to the newfile server apparatus 4.

The terminology and the outline of the file system handled by the newfile server apparatus 4 in the embodiment of the present invention shallbe explained with reference to FIG. 2. When managing files with ageneral purpose file server apparatus, a structure called hierarchicaldirectory is used. As shown in FIG. 2, with a root directory being atthe top, several files/directories hierarchically exist under the rootdirectory. Hereafter, the collection of files/directories that belong tothe hierarchical file/directory structure under a single root directoryas shown in FIG. 2 and attribute information forming the structure shallbe called a file system.

The existing file server apparatus 3 and the new file server apparatus 4can control at least one of these file systems. A file system does notnecessarily exist in a single disk, but may be distributed across aplurality of disks. Conversely, a plurality of file systems may bestored in a single disk. However, for the sake of simplifying theexplanation of embodiments of the present invention, descriptions shallbe made as to an example in which one file system is stored in one disk.

FIG. 3 shows the structure of a file system placed on a disk 43 of thenew file server apparatus 4. The file system consists of meta data,which is attribute information that indicates the size of the respectivefiles or the like, directory entry, which is a collection offile/directory names in the directory and actual data which is thesubstance of the file. In the embodiment of this invention, a meta dataregion 431 that stores meta data, a directory entry region 432 whichstores directory entry and an actual data region 433 that stores actualdata exist on the disk 43. In addition, the disk 43 incorporates a logregion 434, which is used by the migration module 444. In the embodimentof this invention, it is noted that the meta data region 431 and the logregion 434 are on the disk 43. But this is not mandatory. These regionsmay also exist on a memory device of the new file server apparatus 4.

The meta data region 431 stores meta data 70 in the number equal to thenumber of files/directories. Each meta data 70 consists of a meta datanumber 71, file type 72, migration-in-progress flag 73, size 74, lastaccess time 75, last update time 76, NFS access right information 77,CIFS access right information 78, and pointers 79. Especially, theaccess right information for NFS 77 is a file attribute information foraccessing files with the NFS protocol, and the CIFS access rightinformation 78 is a file attribute information to access files with theCIFS protocol. Also, the directory entry region 432 has directoryentries 80 in the same number of directories. The directory entry 80controls at least one of the followings, a list of file names in adirectory or directory names.

The meta data number 71 is a unique number within the file system. Afile or a directory indicated by the meta data number 71 is uniquelydetermined within the file system. Files or directories that belong tothe lower ranks of the directory indicated by the meta data number 71are stored in other directory entries 80 that correspond to the metadata number 71, making it possible to grasp the hierarchical structureof files or directories by tracing these information.

The file type 72 incorporates a flag showing, for example, whether theobject indicated by the meta data number 71 is a file or directory. Themigration-in-progress flag 73 is used by the migration module 444. Whena file is in the process of migration, this flag is turned on and whenthe file migration is completed, the flag is turned off. The specificusage of this flag by the migration module 444 will be explained later.The size 74 shows the size of the file. The last access time 75 showsthe latest time when the host 1 or 2 reads or writes the file. The lastupdate time 76 shows the latest time for updating or writing of thefile. The pointer 79 contains physical address information about theactual file or directory stored on the disk 43. If the object indicatedby the meta data 70 is a file, the pointer 79 shows an area of theactual data region 433. In the case of a directory, it shows a block onthe directory entry region 432. There are a plurality of pointers 79 ifthe file size is large and the file is placed in fragments in more thanone region.

The NFS access right information 77 is information necessary when thehost 1 or 2 refers to a file via the NFS processing module 441, and theCIFS access right information 78 is information necessary when the host1 or 2 refers to a file via the CIFS processing module 442. The NFS andCIFS are managed so that they are able to provide respectively differentstipulated information. For example, attribute information includespermission information for restricting the users with access to thefiles. However, the permission information provided by the NFSprocessing modules 341 and 441 have three types of permissioninformation that indicate whether or not the owner of the files couldaccess the files (read, write and execute), whether the group to whichthe files belong could access the files and whether or not other userscould access the files.

On the other hand, the information provided by the CIFS processingmodules 342 and 442 are called Access Control List (ACL), wherebypermission information for multiple users can be set for a file. Forexample, different permission information by individual users can be setsuch that, for example, User A is permitted just to read the file whileUser B is permitted to also write into the file. Thus, the NFSprocessing module 441 and the CIFS processing module 442 handledifferent types of attribute information. Accordingly, the file systemfor the new file service 4 retains two types of information so thatfiles can be accessed from either of the two processing modules.

The directory entry 80 retains a list of names of files/directories thatcome immediately below one directory. The directory entry 80 containspairs of meta data number 71 and file/directory name 81 for all of thefiles and directories under that directory.

While the information, including the meta data 70 that comprise the filesystem explained with reference to FIG. 3 is on the file serverapparatus 4, the existing file server apparatus 3 also has similarinformation. However, the types of information such as those for metadata 70 and the data structure need not be the same for the new fileserver apparatus 4 and the existing file server apparatus 3. Also, theembodiment of the present invention is described on the premise that theexisting file server apparatus 3 and the new file server apparatus 4 areaccessible from either the host 1 or the host 2. However, if there areother devices that allow file access through Novell Netware file accessprotocol, the meta data will independently possess attribute informationunique to that file access protocol.

Next, an outline of the data migration process for migrating data fromthe existing file server apparatus 3 to the new file server apparatus 4will be explained. When the host 1 or 2, or the new file serverapparatus 4 makes an access to files in the existing file serverapparatus 3, the only means to access the files is through the NFSprocessing module 341 or the CIFS processing module 342. On the otherhand, even when the host 1 or the host 2 is to access the new fileserver apparatus 4, the only means to do this is through the NFSprocessing module 341 or the CIFS processing module 342.

Because of this, if the host 1 or the host 2 simply reads files from theexisting file server apparatus 3 and writes the files in the new fileserver apparatus 4, the files are read out via the NFS processing module341 or the CIFS processing module 342, and the files are written in viathe NFS processing module 441 or the CIFS processing module 442.

In this case, because the files are read via the NFS processing module341 or the CIFS processing module 342, problems occur. For example ifthe access is made via the NFS processing module 341, file attributesand access right information unique to CIFS may be lacking. Conversely,if the access is made via the CIFS processing module 342, the fileattributes unique to NFS may be lacking.

Also, when the host 1 or the host 2 writes files into the new fileserver apparatus 4 via the NFS processing module 441 or CIFS processingmodule 442, a problem occurs in that the last update time 76 or the lastaccess time 75 that remains in the file attribute information of theexisting file server apparatus 3 will be changed to the time when thefiles are written in the new file server apparatus 4 by the host 1 orthe host 2. The migration module 444 in accordance with the embodimentof the present invention solves these problems.

Prior to the data migration, the hosts 1 and 2 are connected only to theexisting file server apparatus 3 via the Ethernet switch 5 andperforming input/output processing. When migrating data, first, thehosts 1 and 2 are disconnected from the existing file server apparatus3. More specifically, when the hosts 1 and 2 are using the file systemof the existing file system 3, the file system is unmounted. Then, theinterface 31 of the existing file server apparatus 32 is disconnectedfrom the Ethernet switch 5, while the interface 32 of the existing fileserver apparatus 32 and the interface 42 of the new file serverapparatus are connected. With this, the existing file server apparatus 3is separated from the network, so that accesses to the existing fileserver apparatus 3 can be made only from the new file server apparatus4.

As the new file server apparatus 4 is newly connected to the network,the settings for the IP address of the file server apparatus 4, shareddirectory names (directory names to be referred when the file system isshown to the hosts 1 and 2), and the like are altered to the settings ofthe existing file server apparatus 3. Also, the existing file serverapparatus 3 may not need to be physically disconnected from the networkas in the case of the embodiment of this invention, but the hosts 1 and2 must be arranged so that they cannot access the existing file serverapparatus 3. For example, this can be done by changing the IP address ofthe existing file server apparatus 3.

Subsequently, the file system of the new file server apparatus 4 ismounted on the hosts 1 and 2 which resume I/O processing. The migrationmodule 444 sequentially writes onto the disk 32 of the new file serverapparatus 4 the files from the existing file server apparatus 3, whileat the same time accepting the read-write processing requests from thehosts 1 and 2. Even when the host 1 or 2 performs the I/O processingwith respect to the new file server apparatus 4 during the migration ofdata, the host can freely read and write files into the new file serverapparatus 4 as the migration module 444 will make it appear as if thefiles of the existing file server apparatus 3 exist in the new fileserver apparatus 4.

Next, referring to FIG. 4, the flow of file migration processesperformed by the migration module 444 to migrate files from the existingfile server apparatus 3 to the new file server apparatus 4 will bedescribed. The migration module 444 sequentially copies all of theattribute information of the files/directories starting from the rootdirectory of the existing file server apparatus 3 (Step 1001), and thencopies the actual data of the respective files (Step 1002). In the eventthe host 1 or 2 tries to make a file update while the files andattribute information are being migrated, the operation of the fileupdate is recorded in the log region 434, and at the end of themigration process, the content recorded in the log region 434 isreflected on the files, and the migration process is terminated (Step1003).

The reason for migrating only the file/directory attribute informationin its entirety is because there are generally more accesses to thefile/directory attribute information than to the actual data when thehost 1 or the host 2 access the files/directories. When the host 1and/or the host 2 makes an access to a file/directory, and when therelated files have not been migrated from the existing file serverapparatus 3, the migration module 444 will try to read the files fromthe existing file server apparatus 3. As a result, the response timedeteriorates as viewed from the hosts 1 and 2 if the above procedure isfollowed. The embodiment of present invention employs the method ofinitially migrating all file/directory attribute information. However,if the performance is not of importance, there would be no problem ifthe file/directory attribute information and the actual data aresimultaneously migrated.

The migration process for migrating the file/directory attributes thatcorresponds to Step 1001 in FIG. 4 and the migration process formigrating actual data corresponding to Step 1002 in FIG. 4 shall beexplained sequentially with reference to FIG. 5. First, the flow ofmigration process for migrating the attribute information of thefiles/directories performed by the migration module 444 will bedescribed with reference to FIG. 5. The migration module 444sequentially executes processes in FIG. 5 starting from the rootdirectory of the existing file server apparatus 3.

First, with NFS command, the attribute information of the directory isobtained (Step 2001). For example, in the case of the NFS, the attributeinformation can be acquired with GETATTR command. Next, the attributeinformation of the directory is obtained with CIFS command (Step 2002).In this case, for example, SMBgetattr may be used. In the embodiment ofthe present invention, the size 74 of meta data 70, the last access time75 and the last update time 76 are simultaneously acquired when the NFSaccess right information 77 is acquired in Step 2001. The sequence ofSteps 2001 and 2002 may be reversed.

In Step 2003, the attribute information acquired is written in the metadata region 431 of the disk. In this instance, the migration-in-progressflag 73 in the meta data 70 is turned on. Next, a search is made toverify whether files exist under the directory (Step 2004). Averification can be made, for example, by executing NFS command READDIR,etc. against the existing file server apparatus 3. If any files exist,the process proceeds to Step 2005.

In Step 2005, the NFS attribute information is acquired for all filesunder the directory, upon receiving the search result obtained in Step2004. In the following Step 2006, the CIFS attribute information isacquired on all files under the directory by CIFS command. In Step 2007,the attribute information acquired in Steps 2005 and 2006 are writteninto the meta data region 431. In this case too, themigration-in-progress flag 73 of meta data 70 is turned on as in thecase of Step 2003.

In Step 2008, a search is made to check whether any directory(subdirectory) exists under the directory. If subdirectories exist, themigration process for migrating attribute information of files anddirectories as shown in FIG. 5 is executed for the entire subdirectories(Step 2009). In other words, the process of FIG. 5 will be executedrecursively such that the attribute information of files and directoriesin one file system will be migrated in their entirety by executing theprocess from the root directory. Finally, the process completes wheninformation on names of the files and directories under the directoryobtained through Steps 2004 and 2008 is created and written in as adirectory entry 80 (Step 2010).

Next, the migration process for migrating actual file data is explainedreferring to FIG. 6. As in the case of the migration process formigrating file attribute information in FIG. 5, the migration processstarts from the root directory, and the migration of actual file datafor the entire file system is performed by recursively executing theprocess for the sub directories. First, a verification is made as towhether any files exist under the directory targeted for migration (Step2101). This process is realized as the migration module 444 searches forthe directory entry in the file system.

Next, as for files under the directory, a verification is made (Step2102) as to whether the migration-in-progress flags are on. For fileswhose migration-in-progress flags are on, the actual file data are readfrom the existing file server apparatus 3 (Step 2103), and the actualfile data are written in the new file server apparatus 4 (Step 2104). InStep 2105, for files whose data have been written in the new file serverapparatus 4, their migration-in-progress flags will be turned off. InStep 2106, a verification is made as to whether the migration of allfiles under the directory targeted for migration has been completed. Ifcompleted, the process moves to Step 2107. If there are files that havenot been migrated, the processes from Step 2102 to Step 2105 arerepeated.

In Step 2107, a verification is made as to whether there aresubdirectories under the directory. If any subdirectories exist, themigration of actual file data in FIG. 6 is executed for thesubdirectories (Step 2108). In other words, as in the case of Step 2009in FIG. 5, the migration of actual file data as indicated in FIG. 6 isexecuted from the root directory, and also is executed for thesubdirectories recursively. Thereafter, the migration-in-progress flag73 of the directory is turned off (Step 2109), to complete the process.If there is no subdirectory found in Step 2107, the process proceedsdirectly to Step 2109 to end the process after turning off themigration-in-progress flag.

Next, a description is made as to the flow of process performed by themigration module 444 when a file access is made from the host 1 or thehost 2 during the migration process of FIGS. 5 and 6. First, referringto FIG. 7, a description is made as to the flow of process when a readrequest to read files or file attributes is issued from the host 1 orthe host 2 during the migration process. When a file access is made fromthe host 1 or the host 2, the NFS processing module 441 or the CIFSprocessing module 442 of the new file server apparatus 4 processes thefile access by using the file system section 443. But during a migrationprocess, the file access is processed via the migration module 444.

When the migration module 444 receives a file access request from theNFS processing module 441 or the CIFS processing module 442, themigration module 444 first conducts a search in the meta data region 431and the directory entry region 432 within the disk 43 of the new fileserver apparatus 4 (Step 2501), and a search in the log region 434 todetermine whether the file attribute information being accessed has beenmigrated to the new file server apparatus 4 (Step 2502). The migrationmodule 444 records in the log region 434 the contents when the host 1 orthe host 2 requests to create or update files during the migrationprocess. This process is explained later.

From the results of Steps 2501 and 2502, a determination is made as towhether the attribute information of the file targeted for access hasbeen migrated to the new file server apparatus 4 (Step 2503). If theattribute information has not been migrated, Step 2510 is performed, andthe migration module 444 reads the file attributes and data from theexisting file server apparatus 3 (Step 2510), and terminates the processafter the results are returned to the host 1 or the host 2 (Step 2511).

When the attribute information has been migrated to the new file serverapparatus 4, the process moves to Step 2504 to check whether or not themigration-in-progress flag 73 of the file's meta data 70 is on. If theflag is on, the actual data has not been migrated to the new file serverapparatus 4, and thus the actual data is read from the existing fileserver apparatus 3 (Step 2505) and the data read out will be writteninto the new file server apparatus 4 (Step 2506). Moreover, when thereis information pertaining to operations such as update of the file inthe log region 434, this information is reflected in the disk 43 of thenew file server apparatus 4 (Step 2507), and the migration-in-progressflag 73 is turned off (Step 2508) such that the migration of the actualfile data is performed.

Next, the read process is completed upon directly reading the fileattributes and data from the disk 43 of the new file server apparatus 4(Step 2509), and returning the results to the host 1 or the host 2 (Step2511). Also if the flag is off at Step 2504, this indicates that thefile attributes and actual data have been migrated to the new fileserver apparatus 4, and thus Step 2509 is executed to return the resultsto the host 1 or the host 2 (Step 2511), to complete the read processduring the migration.

Next, referring to FIG. 8, a description is made as to the flow ofprocess performed by the migration module 444 when there is a requestfrom the host 1 or the host 2 to update or delete files during themigration process.

When a file access request is received from the NFS processing module441 or the CIFS processing module 442, a search is conducted in the metadata region 431 and the directory entry region 432 (Step 2601), and asearch is conducted in the log region 434 (Step 2602) to see whether ornot the attribute information for the files to be accessed have beenmigrated to the new file server apparatus 4. A determination is made(Step 2603) as to whether the attribute information of the files to beaccessed has been migrated to the new file server apparatus 4. If theattribute information has not been migrated, the process proceeds toStep 2610, and the migration module 444 reads the file attributes anddata from the existing file server apparatus 3.

Next, in Step 2611, the file attributes and actual data read from theexisting file server apparatus 3 and the update contents received fromthe NFS processing module 441 or the CIFS processing module 442 arewritten into the log region 434. The reason why the files and updatecontents are written in the log region instead of immediately reflectingthem in the meta data region 431 is because there may be cases in whichthe update contents cannot be immediately reflected.

For example, when data having the directory structure shown in FIG. 3 isrecorded in the existing file server apparatus 3, and the migration ofattribute information for files and directories under dir_b1 has beencompleted during the migration of the file system to the new file serverapparatus 4, there is a possibility of a state in which the attributeinformation of files and directories under dir_b2 (which corresponds toportions shown in FIG. 2 in dotted lines, where the oval sectionsindicate files and the rectangle sections indicates directories) may nothave been migrated. In this case, for example, if there is a file updaterequest for file4, the meta data for file4 cannot be stored becausethere is no attribute information of dir_b2, which is a directory towhich file4 belongs, in the meta data region 431 and the directory entryregion 432 of the new file server apparatus 4. But even in thissituation, it is necessary to receive the update request from the host 1or the host 2 and to reflect update contents in the new file serverapparatus 4. The update contents are therefore recorded temporarily inthe log region 434, and the contents in the log region 434 will bereflected later in the meta data region 431, etc. of the new file serverapparatus 4.

The process proceeds to Step 2604 if the attribute information of thefiles targeted for access in Step 2603 has been migrated to the new fileserver apparatus 4, and the process checks if the migration-in-progressflags 73 of the meta data 70 of the files are on. If the flags are on,which means that the actual data has not been migrated to the new fileserver apparatus 4, the actual data is read from the existing fileserver apparatus 3 (Step 2605), and the actual data is written in thenew file server apparatus 4 (Step 2606).

Moreover, if update information, etc. for the files exists in the logregion 434, this information is reflected in the disk 43 of the new fileserver apparatus 4 (Step 2607). And, according to the update request,the actual data or the meta data of the files is updated later (Step2608). If the migration-in-progress flags 73 are off, which means thatthe file attributes and actual data have been migrated to the new fileserver apparatus 4, the process proceeds to Step 2608 to write theupdate contents received from the NFS processing module 441 or the CIFSprocessing module 442 into the disk 43 of the new file server apparatus4. After the data update in Step 2608 is completed, themigration-in-progress flags 73 are turned off (Step 2609), and theprocess is terminated upon notifying the host 1 or the host 2 that theupdate process has ended.

Next, a description is made as to the data structure of the log region434 and the process of reflecting the contents recorded in the logregion 434 in the file system (Step 2607 of FIG. 8). When the host 1 orthe host 2 makes update requests to update files/directories, etc.during the file migration process, and the files/directories have notbeen reflected in the new file server apparatus 4, the migration module444 records contents of the update requests as log data 90 in the logregion 434 sequentially from the top of the log region 434 (whichcorresponds to Step 2611 of FIG. 8).

The contents of log data 90 are shown in FIG. 9. Migration-completedflag 91 is a flag that shows that the log data 90 has already beenreflected in the file system of the new file server apparatus 4 throughthe migration module 444. File/directory name 92 indicates a file nameor directory name of the targeted file or directory for which the updaterequest has been made by the host 1 or the host 2 during the filemigration operation. Operation name 93 indicates the type of process atthat particular time. For example, the operation name 93 may indicatewriting, moving or deleting the file. Time 94 indicates the time whenthe request is made. Operation data 95 is the data attached to theprocess at the particular time, and the operation data 95 differsdepending on the type of operation. For example, one of the operationdata 95 may be actual file data when a write request has been made.

The flow of reflection process of reflecting the log data 90 isdescribed with reference to FIG. 10. Referring to FIG. 10, a descriptionis first made as to the process that is performed in the case where theupdate information for files/directories were recorded in the log data90 when requests to read or write the files/directories were receivedduring the migration process in the processes in Step 2507 in FIG. 7 orStep 2607 in FIG. 8.

First, a search is conducted sequentially from the top of the log regionto search log data 90 corresponding to the file/directory names targetedfor accesses (Step 3001). In the next Step 3002, a determination is madeas to whether the migration-completed flag 91 of the log data 90 is off.If the flag is off, the process proceeds to Step 3003 to execute theprocess in accordance with the operation recorded in the log data 90.For example, in the case of a data update, data to be written that isrecorded on the log data 90 will be written over the corresponding file.

Next, in Step 3004, the migration-completed flag 91 is turned on to moveonto to Step 3005. If the migration-completed flag 91 is determined tobe on in Step 3002, Steps 3003 and 3004 are skipped to move to Step3005. In Step 3005, a determination is made as to whether all log datain the log region 434 has been searched. If all log data have not beenretrieved, the process returns to Step 3001. The process is completedwhen all log data have been searched.

Referring to FIG. 11, an explanation is made as to the process thattakes place in Step 1003 of FIG. 4, which is the reflection process ofreflecting the log data 90, which is performed at the end of themigration process. In this process, the contents of all of the log data90 written in the log region 434 are reflected in the file/directory.

A search is first made from the top of the log region for the log data90 (Step 3101). Next, a determination is made (Step 3102) as to whetheror not the migration-completed flag 91 of the log data 90 is off. If theflag is off, the operation recorded in the log data 90 is executed (Step3103), and the migration-completed flag 91 is turned on (Step 3104). Ifthe migration-completed flag 91 is already on, these processes areomitted. If all processes are completed for all of the log data 90 (Step3105), the entire log data 90 in the log region 434 are erased in Step3107 to terminate the process. If the processes for the entire log data90 are not completed, the next log data is searched and the processesfrom Step 3102 are repeated.

In the case of the process shown in FIG. 11, the migration-completedflag 91 may not need to be turned on in Step 3104 because only oneprocess is sequentially performed from the start to the end of the datain the log region 434. However, turning on the flag would be effectivewhen the process is interrupted by some obstruction during the processin FIG. 11. For example, when an obstruction occurs, the reflectionprocess of this log data 90 during the migration process is re-executedafter rechecking the log data 90 from the very beginning of the logregion 434. If the migration-completed flag 91 is not turned on, the logdata 90 with the reflection process completed before the re-executionwill also be processed again. This can be avoided by turning on themigration-completed flag 91.

The embodiment above shows an example of how the file system can bemigrated from the existing file server apparatus to the new file serverapparatus even while receiving accesses from the host computers. But asindicated in the migration processes described with reference to FIGS. 4through 11, the present embodiment enables data migration in evensmaller increments, such as the data migration of specified directories,in addition to the entire file system.

Moreover, the size of the disks (i.e., recording media) at the sourceand destination of migration need not be the same. Migration is possibleif the size of the destination disk is larger than the volume of diskused of the file system at the migration source. Moreover, thisembodiment shows the data migration method between two file serverapparatuses. However, the present invention can also be used to migratea file system to an even larger capacity disk within the same fileserver apparatus if the data volume of the file system in the existingdisk has increased, or when a specified directory needs to be moved to adifferent disk.

The present invention enables a file migration without altering the fileattribute information when migrating files between file serverapparatuses. Consequently, data can be stored in the new file serverapparatus without altering the date information such as the file accesstime. Also, the file attributes of file server apparatuses supportingmultiple file access protocols can be migrated.

While the description above refers to particular embodiments of thepresent invention, it will be understood that many modifications may bemade without departing from the spirit thereof The accompanying claimsare intended to cover such modifications as would fall within the truescope and spirit of the present invention.

The presently disclosed embodiments are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims, rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

1. A first file server in a computer system including at least a hostcomputer and a second file sever, comprising: a migration module thatreads data and attribute information of at least one file stored in thesecond file server; and a second module that operates to store the dataand the attribute information of the at least one file read out from thesecond file server in the first file server without changing contents ofthe attribute information, wherein the migration module obtains theattribute information of a directory of the second file server using NFScommand and CIFS command, and verifying whether files exist under thedirectory, wherein if any files exist, the migration module acquires aNFS attribute information for each of the files under the directory, andacquires a CIFS attribute information for each of the files under thedirectory, and wherein when the host computer reads the at least onefile after the second module stored the at least one file in first fileserver, the at least one file stored in the first file server is read.2. The computer system including the first file server according toclaim 1, wherein the attribute information of the file includes at leastdate when the file is created, date when the file is referred, and datewhen the file is updated.
 3. A file migration method for migrating datain a computer system including at least one computer, and a plurality offile servers each having a storage device, the file migration methodcomprising: obtaining by a migration module attribute information of adirectory of a first file server using NFS command and CIFS command;verifying by the migration module whether files exist under thedirectory, wherein if any files exist, obtaining by the migration modulea NFS attribute information for files under the directory, and obtainingby the migration module a CIFS attribute information for files under thedirectory is obtained; storing the obtained attribute information in astorage device of a second file server; and storing in the storagedevice of the second file server actual data of the file read from thestorage device of the first file server according to the attributeinformation of the file.
 4. The file migration method according to claim3, wherein the attribute information of the file includes at least oneof date when the file is created, date when the file is referred, anddate when the file is updated, which are stored in the storage device ofthe first file server.
 5. The file migration method according to claim3, wherein when the computer issues an access request to access a filethat is being migrated while at least one of attribute information ofthe file and actual data of the file is being migrated, a content of theaccess request is stored in a log region of the second file server, anda process according to the content stored in the log region is performedafter the file has been migrated.
 6. The file migration method accordingto claim 3, wherein the second file server accommodates at least onefile access protocol, and attribute information of the file is storedaccording to each of the at least one file access protocol.
 7. The filemigration method according to claim 6, wherein the second file serveraccommodates a plurality of file access protocols, and attributeinformation of the file is stored according to each of the plurality offile access protocols.
 8. The file migration method according to claim3, wherein the first file server is an existing file server and thesecond file server is a new file server, and files stored in theexisting file server are migrated to the new file server.
 9. A filemigration method for migrating data in a computer system including atleast one host computer, an existing first file server and a new secondfile server, each of the first file server and the second file serverhaving a storage device, the file migration method comprising: obtainingby a migration module attribute information of a directory of a firstfile server using NFS command and CIFS command; verifying by themigration module whether files exist under the directory, wherein if anyfiles exist, obtaining by the migration module a NFS attributeinformation for files under the directory, and obtaining by themigration module a CIFS attribute information for files under thedirectory is obtained; obtaining actual data of files from the storagedevice of the first file server and storing in the storage device of thesecond file server the actual data of the files read from the storagedevice of the first file server according to the attribute informationstored in the storage device of the second file server.
 10. The filemigration method according to claim 9, further comprising, after thesteps of the step of reading the attribute information of the directory,the step of reading attribute information of the files from the storagedevice of the first file server according to the first file accessprotocol and the second file access protocol.
 11. The file migrationmethod according to claim 10, wherein the steps of storing the actualdata of the files from the storage device of the first server accordingto the first file access protocol and the second file access protocolare conducted after the steps of reading the attribute information ofthe files according to the first file access protocol are completed. 12.The file migration method according to claim 10, wherein the actual dataof the files are stored in the storage device of the second file serverafter all the attribute information are stored in the storage device ofthe second file server.
 13. The file migration method according to claim10, wherein the attribute information of the files includes at least oneof date when the files are created, date when the files are referred,and date when the files are updated, which are stored in the storagedevice of the first file server.
 14. The file migration method accordingto claim 10, wherein when the host computer issues an access request toaccess a file that is being migrated while at least one of attributeinformation of the file and actual data of the file is being migrated, acontent of the access request is stored in a log region of the storagedevice of the second file server, and a process according to the contentstored in the log region is performed after the file has been migratedfrom the first file server to the second file server.
 15. The migrationmethod according to claim 9, further comprising the step of readingattribute information of subdirectories under the directory according tothe first file access protocol and storing the read attributeinformation of the subdirectories in the storage device of the secondfile server.
 16. The migration method according to claim 9, furthercomprising the step of reading attribute information of subdirectoriesunder the directory according to the second file access protocol andstoring the read attribute information of the subdirectories in thestorage device of the second file server.
 17. A file migration methodfor migrating date in a computer system including at least one hostcomputer and at least one existing file server, the file migrationmethod comprising the steps of: disconnecting the existing file serverfrom the computer system; adding a new file server and connecting theexisting file server to the new file server; obtaining by a migrationmodule attribute information of a directory of the existing server usingNFS command and CIFS command; verifying by the migration module whetherfiles exist under a directory, wherein if any files exist, obtaining bythe migration module a NFS attribute information for files under thedirectory, and obtaining by the migration module a CIFS attributeinformation for files under the directory is obtained; reading out adirectory tree structure of the existing file server and storing thedirectory tree structure in the new file server; reading out all datafiles in the existing file server and successively writing the datafiles into the new file server according to the directory treestructure.
 18. The file migration method according to claim 17, whereinthe step of reading out the directory tree structure includes the stepsof reading out attribute information for files from the existing fileserver and writing the attribute information into the new file serverwithout changing the attribute information.
 19. The file migrationmethod according to claim 18, wherein the attribute information of thefiles includes at least one of date when the files are created, datewhen the files are referred, and date when the files are updated, whichare stored in the storage device of the existing file server.
 20. Thefile migration method according to claim 19, wherein when the hostcomputer issues an access request to access a file that is beingmigrated while at least one of attribute information of the file andactual data of the file is being migrated, a content of the accessrequest is stored in a log region of the new file server, and a processaccording to the content stored in the log region is performed after thefile has been migrated.
 21. The file migration method according to claim17, further comprising, after the step of reading out the attributeinformation, the step of reading the files from the existing file serverand storing the files in the new file server according to the attributeinformation.
 22. The file migration method according to claim 21,wherein the new file server accommodates a plurality of file accessprotocols, and the attribute information of the files is storedaccording to each of the plurality of file access protocols.
 23. A firstfile server in a computer system including at least a host computer anda second file sever, comprising: a migration module that reads data andattribute information of at least one file stored in the second fileserver; and a second module that operates to store the data and theattribute information of the at least one file read out from the secondfile server in the first file server without changing contents of theattribute information, wherein the migration module obtains theattribute information of a directory of the second file server using NFScommand and CIFS command, and verifying whether files exist under thedirectory, wherein if any files exist, the migration module acquires aNFS attribute information for each of the files under the directory, andacquires a CIFS attribute information for each of the files under thedirectory; wherein when the host computer issues a read request to reada first file or file attribute information of the first file duringmigration process, the migration module determines whether the attributeinformation of the first file has been migrated to the first fileserver, wherein, if the attribute information has not been migrated, themigration module reads the attribute information and data of the firstfile from the second file server, if the attribute information has beenmigrated, the migration module further determines whether data of thefirst file has been migrated, wherein in the case data of the first filehas not been migrated, the migration module reads the data of the firstfile from the second file server, and writes the data of the first fileinto the first file server, the migration module then reads attributeinformation and data of the first file from the first file server;wherein in the case data of the first file has been migrated, themigration module then reads attribute information and data of the firstfile from the first file server.
 24. A first file server in a computersystem including at least a host computer and a second file sever,comprising: a migration module that reads data and attribute informationof at least one file stored in the second file server; and a secondmodule that operates to store the data and the attribute information ofthe at least one file read out from the second file server in the firstfile server without changing contents of the attribute information,wherein the migration module obtains the attribute information of adirectory of the second file server using NFS command and CIFS command,and verifying whether files exist under the directory, wherein if anyfiles exist, the migration module acquires a NFS attribute informationfor each of the files under the directory, and acquires a CIFS attributeinformation for each of the files under the directory; wherein when thehost computer issues a request to delete or update a first file duringmigration process, the migration module determines whether attributeinformation of the first file has been migrated to the first fileserver; wherein, if the attribute information has not been migrated, themigration module reads the file attribute information and data of thefirst file from the second file server, and writes and updates theattribute information and data of the first file in a log region, if theattribute information of the file has been migrated, the migrationmodule further determines whether the data of the first file has beenmigrated, wherein in the case the data of the first file has not beenmigrated, the migration module reads data of the first file from thesecond file server, and writes and updates the data of the first file tothe first file server.
 25. A file migration method for migrating data ina computer system including at least one computer, and a plurality offile servers each having a storage device, the file migration methodcomprising: obtaining by a migration module attribute information of adirectory of a first file server using NFS command and CIFS command:verifying by the migration module whether files exist under thedirectory, wherein if any files exist, obtaining by the migration modulea NFS attribute information for files under the directory, and obtainingby the migration module a CIFS attribute information for files under thedirectory is obtained; storing the obtained attribute information in astorage device of a second file server; and storing in the storagedevice of the second file server actual data of the file read from thestorage device of the first file server according to the attributeinformation of the file; wherein when the computer issues a read requestto read a first file or file attribute information of the first fileduring migration process, further comprising: determining by themigration module whether the attribute information of the first file hasbeen migrated to the second file server, wherein if the attributeinformation has not been migrated: reading by the migration module theattribute information and data of the first file from the first fileserver; wherein if the attribute information has been migrated:determining by the migration module whether data of the first file hasbeen migrated; wherein in the case data of the first file has not beenmigrated: reading by the migration module the data of the first filefrom the first file server, and writing the data of the first file intothe second file server, and reading attribute information and data ofthe first file from the second file server; wherein in the case data ofthe first file has been migrated: reading by the migration moduleattribute information and data of the first file from the second fileserver.
 26. A file migration method for migrating data in a computersystem including at least one computer, and a plurality of file serverseach having a storage device, the file migration method comprising:obtaining by a migration module attribute information of a directory ofa first file server using NFS command and CIFS command: verifying by themigration module whether files exist under the directory, wherein if anyfiles exist, obtaining by the migration module a NFS attributeinformation for files under the directory, and obtaining by themigration module a CIFS attribute information for files under thedirectory is obtained; storing the obtained attribute information in astorage device of a second file server; and storing in the storagedevice of the second file server actual data of the file read from thestorage device of the first file server according to the attributeinformation of the file; wherein when the computer issues a request todelete or update a first file during migration process, furthercomprising: determining by the migration module whether attributeinformation of the first file has been migrated to the second fileserver; wherein, if the attribute information has not been migrated:reading by the migration module the file attribute information and dataof the first file from the first file server, and writing and updatingthe attribute information and data of the first file in a log region,wherein if the attribute information of the file has been migrated:determining by the migration module whether the data of the first filehas been migrated, wherein in the case the data of the first file hasnot been migrated: reading by the migration module data of the firstfile from the first file server, and writing and updating the data ofthe first file to the second file server.
 27. A file migration methodfor migrating data in a computer system including at least one hostcomputer, an existing first file server and a new second file server,each of the first file server and the second file server having astorage device, the file migration method comprising: obtaining by amigration module attribute information of a directory of a first fileserver using NFS command and CIFS command; verifying by the migrationmodule whether files exist under the directory, wherein if any filesexist, obtaining by the migration module a NFS attribute information forfiles under the directory, and obtaining by the migration module a CIFSattribute information for files under the directory is obtained;obtaining actual data of files from the storage device of the first fileserver and storing in the storage device of the second file server theactual data of the files read from the storage device of the first fileserver according to the attribute information stored in the storagedevice of the second file server; wherein when the host computer issuesa read request to read a first file or file attribute information of thefirst file during migration process, further comprising: determining bythe migration module whether the attribute information of the first filehas been migrated to the second file server, wherein if the attributeinformation has not been migrated: reading by the migration module theattribute information and data of the first file from the first fileserver; wherein if the attribute information has been migrated:determining by the migration module whether data of the first file hasbeen migrated; wherein in the case data of the first file has not beenmigrated: reading by the migration module the data of the first filefrom the first file server, and writing the data of the first file intothe second file server, and reading attribute information and data ofthe first file from the second file server; wherein in the case data ofthe first file has been migrated: reading by the migration moduleattribute information and data of the first file from the second fileserver.
 28. A file migration method for migrating data in a computersystem including at least one host computer, an existing first fileserver and a new second file server, each of the first file server andthe second file server having a storage device, the file migrationmethod comprising: obtaining by a migration module attribute informationof a directory of a first file server using NFS command and CIFScommand; verifying by the migration module whether files exist under thedirectory, wherein if any files exist, obtaining by the migration modulea NFS attribute information for files under the directory, and obtainingby the migration module a CIFS attribute information for files under thedirectory is obtained; obtaining actual data of files from the storagedevice of the first file server and storing in the storage device of thesecond file server the actual data of the files read from the storagedevice of the first file server according to the attribute informationstored in the storage device of the second file server; wherein when thehost computer issues a request to delete or update a first file duringmigration process, further comprising: determining by the migrationmodule whether attribute information of the first file has been migratedto the second file server; wherein, if the attribute information has notbeen migrated: reading by the migration module the file attributeinformation and data of the first file from the first file server, andwriting and updating the attribute information and data of the firstfile in a log region, wherein if the attribute information of the filehas been migrated: determining by the migration module whether the dataof the first file has been migrated, wherein in the case the data of thefirst file has not been migrated: reading by the migration module dataof the first file from the first file server, and writing and updatingthe data of the first file to the second file server.
 29. A filemigration method for migrating date in a computer system including atleast one host computer and at least one existing file server, the filemigration method comprising the steps of: disconnecting the existingfile server from the computer system; adding a new file server andconnecting the existing file server to the new file server; obtaining bya migration module attribute information of a directory of the existingserver using NFS command and CIFS command; verifying by the migrationmodule whether files exist under a directory, wherein if any filesexist, obtaining by the migration module a NFS attribute information forfiles under the directory, and obtaining by the migration module a CIFSattribute information for files under the directory is obtained; readingout a directory tree structure of the existing file server and storingthe directory tree structure in the new file server; reading out alldata files in the existing file server and successively writing the datafiles into the new file server according to the directory treestructure; wherein when the host computer issues a read request to reada first file or file attribute information of the first file duringmigration process, further comprising: determining by the migrationmodule whether the attribute information of the first file has beenmigrated to the new file server, wherein if the attribute informationhas not been migrated: reading by the migration module the attributeinformation and data of the first file from the existing file server;wherein if the attribute information has been migrated: determining bythe migration module whether data of the first file has been migrated;wherein in the case data of the first file has not been migrated:reading by the migration module the data of the first file from thefirst file server, and writing the data of the first file into thesecond file server, and reading attribute information and data of thefirst file from the new file server; wherein in the case data of thefirst file has been migrated: reading by the migration module attributeinformation and data of the first file from the new file server.
 30. Afile migration method for migrating date in a computer system includingat least one host computer and at least one existing file server, thefile migration method comprising the steps of: disconnecting theexisting file server from the computer system; adding a new file serverand connecting the existing file server to the new file server;obtaining by a migration module attribute information of a directory ofthe existing server using NFS command and CIFS command; verifying by themigration module whether files exist under a directory, wherein if anyfiles exist, obtaining by the migration module a NFS attributeinformation for files under the directory, and obtaining by themigration module a CIFS attribute information for files under thedirectory is obtained; reading out a directory tree structure of theexisting file server and storing the directory tree structure in the newfile server; reading out all data files in the existing file server andsuccessively writing the data files into the new file server accordingto the directory tree structure; wherein when the host computer issues arequest to delete or update a first file during migration process,further comprising: determining by the migration module whetherattribute information of the first file has been migrated to the newserver; wherein, if the attribute information has not been migrated:reading by the migration module the file attribute information and dataof the first file from the existing file server, and writing andupdating the attribute information and data of the first file in a logregion, wherein if the attribute information of the file has beenmigrated: determining by the migration module whether the data of thefirst file has been migrated, wherein in the case the data of the firstfile has not been migrated: reading by the migration module data of thefirst file from the existing file server, and writing and updating thedata of the first file to the new file server.